Process of producing carbodimides



instances, t Y v t. sarb di m dsants be a 12, 4 ,81 I PRoeEssonnnonucnsecannommmns Roti'ert' F. Cole'S,,Nortli staPhuhjMihng assignon. to General Aniline & Film Corporation; New York, N.' Y., a

corporation-ofDelawar-e i This; invention: relates to carhodiimidesand a process forprepan'ng them.

carbodiimides; are: known chemicalcompoundsand are useful intermediates: in* the chemical held: and re l'ated arts; Carbodiimides have been found particularly valuable hr the: realm of plmtogra'phy'where: they: are I used to prepare-modified gelatinsand'lin: this. connection reference is: made; to: my co-pending application; Serial Nos 609,529, filed- September 1:3;(12956, now abandoned;

It'is known to-prepare carbodiimideszby treating NN' disubstitutedithibureas withiheavy metal oxides orcarbo nates'such as mercuric oxide HgO), lead oxide (PbO), lead carbonate PIJ'CQ JQ-and 'the like; Tn the ensuing reaction, the elements of: hydrogenrsu'lfidej are abstracted from the thiourea resulting in formation of the corresponding carbodiimides. A'se'rions dhawback, however,

to the above described process, can be attributed to the inconsistent results. are often obt-ainedr Insome iih It WhiIe a 9: t j la a r li flatw atiees r is generally conceded that the action of the aforesaid heavy metal compound on.-N,N--disubstituted thioureas,

of mercuric oxide. It is to be noted th'fa wherein the elements hydrogen sulfide are abstracted, is I:

a surface phenomenon occurring at a reactive surface. If the reactive surface of the heavy metal compounds is deactivated before complete desulfurization of the thioureas is complete, such as the deposition of a metal sulfide as a coating over the heavy metal compounds, then the rate of desulfurization is retarded and the yields of carbodiimides correspondingly low. In addition, it is diflicult to procure or obtain the heavy metal compounds which always possess the same degree of surface activity I so that one obtains high yields of a particular carbodiimide in one instance while the same carbodiimide may be obtained in low, yields at another time using a, different source or mode of preparation of the heavy metal compounds. I H

It it, therefore, believedto be evident that a need exists in the art for the production of carbodiimides in higher yields and withgreater reliability and a provision of such a process constitutes the object and purpose "of the present invention. 7 i

It has now been discovered that carbodiimides can be produced in higher yields andwith greater dependability by reacting N,N-'disubstituted thioureas with a mercury complex in the presence of a water soluble inorganic base such as KOH, NaOH, LiOH, etc. The reaction The mercury complex or mercuric potassium iodide 'N-(B-bromoallyl)-N-propylthiourea N-(fl bromoallyl) -N'-isopropylthiourea I aforesaidv disubstituted comprises two steps, (1) formation ,of the mercury com- I 'plex, (2) treatment of the N,N'-disubstituted thiourea V can b'ei repre'sentei by the' following general "i j wherein A; and haverthesvahiesi girenlabmei v 1 Ratsat Ma e 5 5 shown in the .e llation- -is; ai imwna compound ,im flle chemical art and; is; SQmBimF$1r3emd\ ho as.- Meyers reagent (to. Haekhs. Chemicai Dietionarnii by Grant; third edition, pp. 524-525). V t

Since potassium iodide is formedas a by-prpdueh of the above reaction, thisv latter compound can paused in less than the required amount to com' jl ex ride can'be used in lieu of'mercuricoxide v potassium hydroxide mustt-bea added to the reactionisince the formationof, carbodiimidesias above described, requires the presence ofalkalil & 1" 1 H The N,N"-disubstimted carbodiimides pnepared im am cordancewith the present inventiomean be represented by:the:followinggeneratformula: I "I I A,-N'---=C ---NIv-B1 I wherein; A and -B',,which be; alikeior diflerentg; represent organic radicals: such as: am aliphatic-radical, i253; alkyl, e:.g., methyl, ethyl; propyl',. isopropylgn-bntylgsisoa butyl; tertz-butyl; allfyl, crotyl fiahydrroxyethydij-y-ldimeths ylaminopropyl, 51-br0moa1ly1, and like; am'alicyelie radicals. e.g., cyclopropyl, eyclobirtyl cyclopentatl, cycle hexyl cyclolieptyh. cyelooctylgfcyclononyl, :cyclodecyl; and the like. a a

The N,N'-disubstituted' thioureas used as intermediates for" the preparation: oficarbodiimiaes as herein deseribed n s H In the following list are typifiedrfsbllNi't-disflb bed thioureas which may befiemployedfqr the purpose herein 35 I a i v 7 .set forth:

' N-methyl-N-propylthiourea N-propyl-N tert.-butylthiourea N-isopropyl-N' terL-butylthiourea N- -dimethylaminopropyl) -N-tert.-butylthiourea N- B-bromo allyl) -N'- tert-.ebutylthiourea N-( y-dimethylaminopropyl)-N'-(,8-bromoallyl)thiourea Of the carbodiimides which canibe prepared from the thioureas, the followinglist is typical; I I

N-methyl-N'-tert.-butylcarbodiimide' N,N'-diisopropylcarbodiimide v N,N-dicyclohexylcarbodiimide N,N'-ditert.-butylcarbodiimide N-cyclohexyl-N'-tert.-butylcarbodiimide N,N'-dibutylcarbodiimide N,N'-Idiisobutylcarbddiimide I N-allyl-N-propylcarbodiimide N,N-diallylcarbodiimide is N-allyl-N cyclohexylcarbodiimide a N-methyl-N' propylcarbodiimide Theginvention is illustrated in greater detail by the following specific. examples but it is to be understoodihat such examples are illustrative only and are not to be taken as imposing limitation on the invention.

EXAMPLE I i N,N-dicyclohexylcarbodiimide In aj 2-liter, 3-neck'ed flask, equipped with a stirrer and condenser was placed a solution of potassium iodide (332 g., 2 mol) in -1-liter of warm water and then (135.7 g., 0.5 mol) of mercuric chloride. As soon as the solution was complete, potassium hydroxide (57 g., 1.0.mol wasa'dded. The resulting solution was treated with N,N-dicyclohexylthiourea (120 g., 0.5 mol). The suspension was heated at reflux for 4 hours. The mercuric sulfidewas removed by filtration and washed well with petroleum ether (B.P. 30-60 C.). The organic layer was separated, dried and distilled at reduced pressure. Yield 72.5 g., 70%, 13.1. 154-155 C./11 mm.

EXAMPLE II Thcisame procedure was employed as given above for Example I except that N,N-diisopropylthiourea was used. The N,N'-diisopropylcarbodiimide so obtained boiled at 3637 C., at mm.

I claim: 1. A process of producing a lowing general I formula:

carbodiimide of the 01- ,946,819 in V v wherein A and B are selected from the class consisting of lower 'alkyl, lower cycloalkyl and phenyl which comprises reacting about 1 mole of a N,N'-dis-ubstituted thiourea of the following general formula:

ANCNLB l wherein A and B are selected from the class consisting of lower alkyl, lower cycloalkyl and phenyl with about 1 mole of mercuric potassium iodide andabout 2 moles of an alkali metal hydroxide in an aqueous medium and separating the carbodiimide formed from said aqueous medium. 7 a

2. A process as defined in claim 1 wherein the alkali metal hydroxide is potassium hydroxide.

3. A process of producing N,N-dicyclohexyl carbodiimide which comprises refluxing in aqueous medium about 1 mole of N,N'-dicyclohexylthiourea with about 2 moles of sodium hydroxide and '1 mole of mercuric potassium iodide, separating the oily liquid formed from said aqueous solute medium and recovering the pure N,N- V

dicyclohexyl carbodiimide by distillation.

4. A process of producing N,N'-diisopropyl carbodiimide 'WhiCh comprises refluxing in aqueous medium about 1 mole of'N,N'-diisopropylthiourea with about 2 moles of sodium hydroxide and 1 mole of mercuric potassium iodide, separating the other liquid formed from said aqueous solute medium and recovering the pure N,N'-diis0propyl carbodiimide by distillation.

Germany Mar. 7', 1955 

1. A PROCESS OF PRODUCING A CARBODIIMIDE OF THE FOLLOWING GENERAL FORMULA: 